Upstream Router Detection for RPF (2) Solutions

Operational approach to avoid mismatches
Restrict the PIM domain to an IGP domain.
All IGPs use link-local addresses to recognize each neighbor.
-> global gateways do not appear in the routing table.
A static route must use a link-local gateway.
Do not assign multiple link-local addresses on a single interface.

Another possible solution
Introduce a mechanism to resolve link-local addresses corresponding to given global addresses.
We would not have to care mismatches with this approach.
ICMPv6 node information messages could be used.
Need further study and runnging code.